/*
 * SVG Salamander
 * Copyright (c) 2004, Mark McKay
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 *   - Redistributions of source code must retain the above 
 *     copyright notice, this list of conditions and the following
 *     disclaimer.
 *   - Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials 
 *     provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE. 
 * 
 * Mark McKay can be contacted at mark@kitfox.com.  Salamander and other
 * projects can be found at http://www.kitfox.com
 *
 * Created on January 26, 2004, 8:40 PM
 */

package com.kitfox.svg.pathcmd;

//import org.apache.batik.ext.awt.geom.ExtendedGeneralPath;
import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.Arc2D;
import java.awt.geom.GeneralPath;

/**
 * This is a little used SVG function, as most editors will save curves as
 * Beziers. To reduce the need to rely on the Batik library, this functionallity
 * is being bypassed for the time being. In the future, it would be nice to
 * extend the GeneralPath command to include the arcTo ability provided by
 * Batik.
 *
 * @author Mark McKay
 * @author <a href="mailto:mark@kitfox.com">Mark McKay</a>
 */
public class Arc extends PathCommand {

	public float rx = 0f;
	public float ry = 0f;
	public float xAxisRot = 0f;
	public boolean largeArc = false;
	public boolean sweep = false;
	public float x = 0f;
	public float y = 0f;

	/** Creates a new instance of MoveTo */
	public Arc() {
	}

	public Arc(boolean isRelative, float rx, float ry, float xAxisRot,
			boolean largeArc, boolean sweep, float x, float y) {
		super(isRelative);
		this.rx = rx;
		this.ry = ry;
		this.xAxisRot = xAxisRot;
		this.largeArc = largeArc;
		this.sweep = sweep;
		this.x = x;
		this.y = y;
	}

	// public void appendPath(ExtendedGeneralPath path, BuildHistory hist)
	@Override
	public void appendPath(GeneralPath path, BuildHistory hist) {
		float offx = isRelative ? hist.lastPoint.x : 0f;
		float offy = isRelative ? hist.lastPoint.y : 0f;

		arcTo(path, rx, ry, xAxisRot, largeArc, sweep, x + offx, y + offy,
				hist.lastPoint.x, hist.lastPoint.y);
		// path.lineTo(x + offx, y + offy);
		// hist.setPoint(x + offx, y + offy);
		hist.setLastPoint(x + offx, y + offy);
		hist.setLastKnot(x + offx, y + offy);
	}

	@Override
	public int getNumKnotsAdded() {
		return 6;
	}

	/**
	 * Adds an elliptical arc, defined by two radii, an angle from the x-axis, a
	 * flag to choose the large arc or not, a flag to indicate if we increase or
	 * decrease the angles and the final point of the arc.
	 *
	 * @param rx
	 *            the x radius of the ellipse
	 * @param ry
	 *            the y radius of the ellipse
	 *
	 * @param angle
	 *            the angle from the x-axis of the current coordinate system to
	 *            the x-axis of the ellipse in degrees.
	 *
	 * @param largeArcFlag
	 *            the large arc flag. If true the arc spanning less than or
	 *            equal to 180 degrees is chosen, otherwise the arc spanning
	 *            greater than 180 degrees is chosen
	 *
	 * @param sweepFlag
	 *            the sweep flag. If true the line joining center to arc sweeps
	 *            through decreasing angles otherwise it sweeps through
	 *            increasing angles
	 *
	 * @param x
	 *            the absolute x coordinate of the final point of the arc.
	 * @param y
	 *            the absolute y coordinate of the final point of the arc.
	 * @param x0
	 *            - The absolute x coordinate of the initial point of the arc.
	 * @param y0
	 *            - The absolute y coordinate of the initial point of the arc.
	 */
	public void arcTo(GeneralPath path, float rx, float ry, float angle,
			boolean largeArcFlag, boolean sweepFlag, float x, float y, float x0,
			float y0) {

		// Ensure radii are valid
		if (rx == 0 || ry == 0) {
			path.lineTo(x, y);
			return;
		}

		if (x0 == x && y0 == y) {
			// If the endpoints (x, y) and (x0, y0) are identical, then this
			// is equivalent to omitting the elliptical arc segment entirely.
			return;
		}

		Arc2D arc = computeArc(x0, y0, rx, ry, angle, largeArcFlag, sweepFlag,
				x, y);
		if (arc == null) {
			return;
		}

		AffineTransform t = AffineTransform.getRotateInstance(
				Math.toRadians(angle), arc.getCenterX(), arc.getCenterY());
		Shape s = t.createTransformedShape(arc);
		path.append(s, true);
	}

	/**
	 * This constructs an unrotated Arc2D from the SVG specification of an
	 * Elliptical arc. To get the final arc you need to apply a rotation
	 * transform such as:
	 * 
	 * AffineTransform.getRotateInstance (angle, arc.getX()+arc.getWidth()/2,
	 * arc.getY()+arc.getHeight()/2);
	 */
	public static Arc2D computeArc(double x0, double y0, double rx, double ry,
			double angle, boolean largeArcFlag, boolean sweepFlag, double x,
			double y) {
		//
		// Elliptical arc implementation based on the SVG specification notes
		//

		// Compute the half distance between the current and the final point
		double dx2 = (x0 - x) / 2.0;
		double dy2 = (y0 - y) / 2.0;
		// Convert angle from degrees to radians
		angle = Math.toRadians(angle % 360.0);
		double cosAngle = Math.cos(angle);
		double sinAngle = Math.sin(angle);

		//
		// Step 1 : Compute (x1, y1)
		//
		double x1 = (cosAngle * dx2 + sinAngle * dy2);
		double y1 = (-sinAngle * dx2 + cosAngle * dy2);
		// Ensure radii are large enough
		rx = Math.abs(rx);
		ry = Math.abs(ry);
		double Prx = rx * rx;
		double Pry = ry * ry;
		double Px1 = x1 * x1;
		double Py1 = y1 * y1;
		// check that radii are large enough
		double radiiCheck = Px1 / Prx + Py1 / Pry;
		if (radiiCheck > 1) {
			rx = Math.sqrt(radiiCheck) * rx;
			ry = Math.sqrt(radiiCheck) * ry;
			Prx = rx * rx;
			Pry = ry * ry;
		}

		//
		// Step 2 : Compute (cx1, cy1)
		//
		double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
		double sq = ((Prx * Pry) - (Prx * Py1) - (Pry * Px1))
				/ ((Prx * Py1) + (Pry * Px1));
		sq = (sq < 0) ? 0 : sq;
		double coef = (sign * Math.sqrt(sq));
		double cx1 = coef * ((rx * y1) / ry);
		double cy1 = coef * -((ry * x1) / rx);

		//
		// Step 3 : Compute (cx, cy) from (cx1, cy1)
		//
		double sx2 = (x0 + x) / 2.0;
		double sy2 = (y0 + y) / 2.0;
		double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
		double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);

		//
		// Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
		//
		double ux = (x1 - cx1) / rx;
		double uy = (y1 - cy1) / ry;
		double vx = (-x1 - cx1) / rx;
		double vy = (-y1 - cy1) / ry;
		double p, n;
		// Compute the angle start
		n = Math.sqrt((ux * ux) + (uy * uy));
		p = ux; // (1 * ux) + (0 * uy)
		sign = (uy < 0) ? -1d : 1d;
		double angleStart = Math.toDegrees(sign * Math.acos(p / n));

		// Compute the angle extent
		n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
		p = ux * vx + uy * vy;
		sign = (ux * vy - uy * vx < 0) ? -1d : 1d;
		double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
		if (!sweepFlag && angleExtent > 0) {
			angleExtent -= 360f;
		} else if (sweepFlag && angleExtent < 0) {
			angleExtent += 360f;
		}
		angleExtent %= 360f;
		angleStart %= 360f;

		//
		// We can now build the resulting Arc2D in double precision
		//
		Arc2D.Double arc = new Arc2D.Double();
		arc.x = cx - rx;
		arc.y = cy - ry;
		arc.width = rx * 2.0;
		arc.height = ry * 2.0;
		arc.start = -angleStart;
		arc.extent = -angleExtent;

		return arc;
	}

	@Override
	public String toString() {
		return "A " + rx + " " + ry + " " + xAxisRot + " " + largeArc + " "
				+ sweep + " " + x + " " + y;
	}
}
